SITE HOME PAGE THE VITAMIN B12 AND FOLATE PATHOLOGY INVESTIGATION SITE HOME PAGE
 THE INVESTIGATION OF ERRORS IN PATHOLOGY TESTS FOR VITAMIN B12 AND FOLATE DEFICIENCY BY MEANS OF MEDICAL EXPERIMENTS
 INTRODUCTION THE SERUM VITAMIN B12 INVESTIGATION THE METHYLMALONIC ACID INVESTIGATION THE HOMOCYSTEINE INVESTIGATION THE HOLOTRANSCOBALAMIN INVESTIGATION THE FOLATE INVESTIGATION REFERENCES AND LINKS B12 AND FOLATE INFORMATION RESPONSES TO INVESTIGATION
 THE SERUM B12 EXPERIMENT - A THE SERUM B12 EXPERIMENT - B SERUM B12 EVIDENCE SERUM B12 ERRORS
 Summary Analytes and Laboratories Objectives Findings
 Method Analysis - CI Analysis - Pxu Analysis - Pab
 Observations Lab Performance
 Results - Notes Notes for Charts and Tables
 Results - Assay Quality
 Conclusions Assay Quality

Derivation of Probability pxu

Source: http://mathworld.wolfram.com/ConfidenceInterval.html, reference AB30

Assuming Normal Distribution of results:

Pxu = ERF(n/SQRT(2))

where

• Pxu = probability result x lies within ± n SD of mean u in figure A
• ERF = error function
• n = specified number of Standard Deviations
• SD = Standard Deviation

Substituting #SD for n and taking absolute value of # SD:

Pxu = ERFC(ABS(#SD)/(SQRT(2)))

where

• Pxu = probability each independent result lies within # SD of either side of mean = either half of area under curve in figure B
• # SD = measured difference between any result and the mean

Taking complement of error function to select area outside of confidence interval:

pxu = ERFC(ABS(#SD)/(SQRT(2)))

where

• pxu = probability any result lies outside # SD of either side of mean = either half of area under curve in figure C
• ERFC = complimentary error function = 1 - ERF

pxu = ERFC(ABS(#SD)/(SQRT(2))) Top of page

This web site is owned, designed and maintained by Paul Henry Golding of Nambour, QLD, Australia. © 2007-2019